Field of the Invention
Solid propellants have numerous advantages over liquids for missile propulsion and as gas generants. Among these are greater safety in storage, handling, and transport, higher density, and simplicity of propellant packaging. Liquids, however, have traditionally offered the huge advantage of ease of throttling and can be extinguished and reignited at will, thereby offering better energy management with minimal waste of on-board propulsive resources.
One application for this invention is in the Divert and Attitude Control Systems (DACS) for kinetic-kill missile warheads. DACS provide for control of vehicles flying outside the earth's atmosphere. Missile DACS typically use solid-propellant gas generators (SPGG) to provide propulsive jets that accelerate and point the vehicle in the vacuum conditions of near-earth space. In the typical existing system, the gas generator is ignited at the start of the control period and continues to burn generally at a measured constant rate for the control duration. This is despite the fact that most of the gas is vented uselessly, because control is needed during only about 30% of the flight. As the flight time increases, the necessary control time remains essentially constant. This means that for longer flight times the wasted fuel increases to over 90%. Matching of the propellant consumption to the control requirement in a DACS could be provided by a multi-ignition, burn-on-command SPGG. This capability would eliminate the biggest single deficiency of solid-propellant systems (controllability after ignition) and would have widespread application potential. The technology involved for gas generators could be extended to most solid-propellant rocket motors as well, resulting in substantial system-level performance benefits.
Some DACS being developed, and other applications for gas generators as well, would benefit from a capability of the gas generator not only to be ignited and extinguished on command, but to have its gas temperature and flow rate controllable. For example, a single, simple gas generator may then be called on to provide turbine drive gases at temperatures around 2000.degree. F., and subsequently provide a greater mass flow of gas at much higher temperatures (3000.degree. F. to 5000.degree. F.) for generating thrust in a rocket nozzle.
In this invention a liquid or gaseous oxidizer is used in relatively small quantities and in novel ways to effect the capabilities discussed above. Nitrous oxide (N.sub.2 O) is a suitable agent for use in this invention, but other agents may be used successfully within the scope of the invention in similar ways. Pertinent characteristics of nitrous oxide are discussed below.